Beta-(ortho-methoxy) phenyl-isopropyl para-methoxybenzyl alkyl amines and salts thereof



Patented Apr. 6, 1954 UNITED STATES PATENT OFFICE Richard V. Heinzelmann, Kalamazoo, Mich, as-

signer to The Upjohn Company, Kalamazoo, Mich, a"corporation of Michigan No Drawing. Application January 21, 1949, Serial No. 72,079

7 Claims.

(I)OH3 CH3 R wherein R is a loWer-alkyl radical containing up to and including four carbon atoms, and to acid addition and quaternary ammonium salts thereof.

It is an object of the present invention to provide a novel series of compounds, having important physiological activity, which are especially useful in therapy as local anesthetics. The compounds are also useful in therapy as anticholinergics, antihistaminics, and for the relaxation of constricted bronchial musculature, i. e., as bronchodialtors. Certain of the quaternary ammonium derivatives are also useful as surfacetension depressants, wetting agents, and the like. The provision of novel compounds having the various above-mentioned utilities is a further object of the invention. Other objects will become apparent hereinafter.

The free bases of the present invention are mobile colorless to pale amber liquids, slightly soluble in Water, soluble in most common organic solvents, such as methanol, ethanol, chloroform, acetone, benzene, and others, and form addition salts with most acids. Representative acid addition salts of the amines which may be prepared are the iormate, acetate, butyr ate, benzoate, succinate, salicylate, citrate, tarether, u

trate, picrate, hydrochloride, hydrobromide, hy-

droiodide, sulfate, phosphate, and the like. A preferred procedure for the preparation of the acid addition salts involves the admixture of anhydrous organic solutions of the amine and the acid in approximately stoichiometric proportions, in which case the salt, which is insoluble in the organic solvent, precipitates substantially as soon as it is formed. Alternatively, stoichiometric proportions of the acid and amine may merely be admixed and the solid salt obtained by evaporation to dryness. Other methods for preparing amine acid addition salts may also be used, and are known to the art.

Various other useful quaternary ammonium salts of the tertiary amines of the invention may also be prepared, as by mixing the amine with an alkyl halide, aralkyl halide, or aryl sulfonic acid ester, heating the mixture, and thereafter separating the quaternary ammonium salt of the amine.

. Among compounds which may be employed in such manner to prepare the quaternary ammonium salts are methyl bromide, ethyl bromide, allyl chloride, cetyl bromide, myristyl bromide, lauryl bromide, benzyl chloride, benzyl bromide, ethyl (para-toluene) -sulfonate, and the like. As before stated, the quaternary ammonium salts thus produced are also useful as surface-tension depressants and wetting agents.

A study of the basic chemical structure of most known synthetic local anesthetics shows them to be tertiary amino-alkyl esters of amino-substituted aromatic acids. For example, some representative known local anesthetics are beta-diethylarninoethyl (para-amino) -benzoate, gamma-dibutylaminopropyl (para-amino)-benzoate, alpha, beta dimethyl gamma dimethylaminopropyl (para amino) benzoate, beta,betadimethyl gamma diet-hylaminopropyl (paraamino)-benzoate, and gamma-(methylpiperidino)-propyl (para-amino)-benzoate. Other local anesthetics oi the prior art are alkyl esters of amino-substituted aromatic acids, e. g., ethyl and butyl (para-amino) -benzoates. In contrast to the foregoing well-known ester-type anesthetics, the novel methoxyphenyl isopropyl paramethoxybenzyl amine derivatives of the present invention have an entirely different structure, and their strong local anesthetic activity is thus entirely unexpected.

When the compounds are desired to be employed as therapeutic agents, a preferred manner of oral administration is in the form of acid addition salts such as the hydrochloride, sulfate, citrate, or acetate, in which case the therapeutic agent may be combined with excipients, diluents or lubricants according to known methods of tabletmanufacture. The amine salts may also be administered as an aqueous or other solution. When the free base is employed as the therapeutic agent, it may be administered by inhalation, as with a nebulizer. When employed as local anesthetics, any suitable method of application known in the art may be employed.

In addition to being useful as local anesthetics, anticholinergics, antihistaminics, and, in the case of certain quaternary ammonium salts, as surface-active agents, the compounds are useful intermediates in the preparation of other therapeutically useful compounds, via, the corresponding ortho-hydrory substituted compounds. This conversion is accomplished, if desired, by demethylation, as with strong acid and heat, evaporation, and isolation of the phenolic amine, either as the free base or a salt thereof, according to conventional procedure.

The free base of the present invention may be prepared by adding para-methoxybenzyl chloride to a suspension of anhydrous sodium carbonate in the particular beta-(ortho-methoxy) phenyl-isopropyl alkyl amine, e. g., the methyl, ethyl, isopropyl, butyl, isobutyl, or tertiary-butyl amine, selected as starting material, while heating the mixture at a temperature of 120 to 150 degrees centigrade over a period of from one to four hours. The isolation is conveniently accomplished by pouring the reaction mixture into water, extracting with benzene, removing the solvent, and fractionally distilling to yield the free amine. Alternatively, the benzene solution may be treated by extracting with dilute aqueous acid, basifying the resulting aqueous solution, extracting with benzene, removing the solvent, dissolving the residue in ethyl acetate, adding hydrogen chloride or other acid in alcohol, e. g., isopropanol, thereto, and recovering the amine as its acid salt. Other conventional methods of preparation, isolation, and purification, both of the free base and of the salts thereof, are satisfactory.

As will be apparent to one skilled in the art, the tertiary amine produced by the preceding process is dependent upon the particular beta- (ortho-methoxy)phenyl-isopropyl alkyl amine used as starting material. Thus, if the alkyl group in the starting secondary amine is the methyl group, the product will be beta-(orthomethoxy)phenyl-isopropyl para-methoxybenzyl methyl amine or a selected salt thereof. Other tertiary amine products which may be obtained in the same manner, depending upon the particular starting material, include beta (ortho methoxy phenyl isopropyl para methoxy benzyl methyl amine, beta (ortho methoxy) phenyl isopropyl para methoxy benzyl ethyl amine, beta (ortho methoxy)phenyl isopropyl para methoxy benzyl propyl amine, beta (ortho methoxy) phenyl isopropyl para methoxy benzyl isopropyl amine, beta (ortho methoxy)phenyl isopropyl para methoxy benzyl butyl amine, beta (ortho methoxy) phenyl isopropyl para methoxy benzyl iso butyl amine, beta (ortho methoxy)phenyl isopropyl para methoxy benzyl secondary butyl amine, beta (ortho methoxy)phenyl isopropyl para methoxy benzyl tertiary butyl amine, and acid addition and quaternary ammonium salts thereof, as disclosed in the foregoing.

The following examples are given to illustrate the present invention but are not to be construed as limiting.

Example 1.-Beta- (ortho-memory) phenyZ- isopropyl isopropyl amine A solution of 8.25 grams of beta-(orthomethoxy)phenyl-isopropyl amine [J Am. Chem. Soc. 60, 465 (1938)], and 3.2 grams of purified acetone in 75 milliliters of absolute ethanol was added to 0.1 gram of Adams platinum catalyst which had been activated by agitation in ethanol under an atmosphere of hydrogen. The suspension was shaken under a hydrogen pressure of about three atmospheres until the reduction was complete, which, in several experiments, usually required from one to four hours. The catalyst was then removed, the residual solution diluted with benzene, and the combined solvents removed. The residual oil, when fractionally distilled, gave beta-(ortho-methoxy)phenyl-isopropyl isopropyl amine, distilling at 126 degrees centigrade at a pressure of ten millimeters of mercury.

The hydrochloride of the free base was prepared by adding ethereal hydrogen chloride to an ether solution of the free base, and collecting the solid hydrochloride after cooling overnight. After two crystallizations from ethanol, the beta-(ortho-methoxy)phenyl-isopropyl isopropyl amine hydrochloride melted at 1727-1731? degrees centigrade.

Analysis:

Calculated for CiaHzzONClt C 64.04 H 9.10 N 5.74 Found: 63.63 8.88 5.72

Example 2.-Beta- (ortho-memory) phenyl-iso- 'propyl para-methozcy-benzyl isopropyl amine Thirty-nine grams of para-methoxybenzyl chloride was added to a stirred suspension of 47 grams of beta- (ortho-methoxy) phenyl-isopropyl isopropyl amine and 44 grams of anhydrous sodium carbonate, heated to about 120 degrees centigrade over a period of about one hour. Heating and stirring were continued for an additional two hours, during which time the temperature was gradually raised to 150 degrees centigrade. The reaction mixture was then cooled, water added, the aqueous suspension extracted with benzene, the benzene layer washed with water and then extracted with dilute hydrochloric acid. Three layers formed, an upper benzene layer, a middle aqueous layer, and a lower oily layer of undissolved amine hydrochloride. The benzene layer was discarded, whereafter the remaining layers were made alkaline with sodium hydroxide and extracted with benzene. The benzene extract was washed with water, the benzene removed and the residue distilled under reduced pressure. There was thus obtained beta- (ortho-mcthoxy) -phenylisopropyl para-methoxybenzyl isopropyl amine, distilling at 229-230 degrees centigrade at a pressure of five millimeters of mercury or at 190-191 degrees centigrade at a pressure of 0.9 millimeter of mercury.

The free base was converted to the hydrochloride by mixing solutions of the free base and hydrogen chloride in anhydrous ether. The resulting oily precipitate, after crystallization from a mixture of ethanol, ethyl acetate and ether, melted at -107 degrees centigrade.

The picrate was also prepared, and when crystallized from ethanol, was found to melt at 113-414 degrees centigrade.

Analysis:

Calculated for C H O N C 58.26 H 5.80 N 10.07 Found: 58.20 5.66 10.12

Example 3.-Beta,- (ortho-memory) phenyl-isopropyl para-methomybenzyl methyl amine Twenty-three and four-tenths grams of paramethoxybenzyl chloride was added to a stirred suspension of 26.8 grams of beta-(ortho-methoxy)phenyl-isopropyl methyl amine and thirty grams of anhydrous sodium carbonate, and heated to about degrees centigrade over a period of about one hour. Heating and stirring were continued for an additional two hours, during which time the temperature was gradually raised to degrees centigrade. The reaction mixture was then cooled, water added, the aqueous suspension extracted with benzene, the benzene layer washed with water and then extracted with dilute hydrochloric acid. Three layers formed, an upper benzene layer, a middle aqueous layer, and a lower oily layer of undissolved amine hydrochloride. The benzene layer was discarded, whereafter the remaining layers were made alkaline with sodium hydroxide and extracted with benzene. The benzene extract was washed with water, the benzene removed, and the residue distilled under reduced pressure. There was thus obtained beta- (ortho-methoxy) phenyl-isopropyl para-methoxybenzyl methyl amine, distilling at 175-181 degrees centigrade at a pressure of 0.08 millimeter of mercury or at 187 degrees centigrade at a pressure of 0.25 millimeter of mercury.

The free base was converted to the hydrochloride salt by mixing solutions of the free base and hydrogen chloride in anhydrous ether. The resulting oily precipitate, after crystallization from a mixture of ethanol, ethyl acetate and ether, gave pure beta-(ortho-methoxy)phenyl-isopropyl para-methoxybenzyl methyl amine hydrochloride, melting at 146-1475 degrees centigrade.

Analysis:

Calculated for C H NCl C 67.94 H 7.80 N 4.17 Found 68.12 7.89 4.34

wherein R is a lower-'alkyl radical containing up to and including four carbon atoms, and (2) acid addition and quaternary ammonium salts thereof.

2. An acid addition salt of a beta-(orthomethoxy)phenyl-isopropyl para-methoxybenzyl alkyl amine of the formula:

OCH;

wherein R is a lower-alkyl radical containing up to and including four carbon atoms.

3. A hydrochloride addition salt of a beta- (ortho-znethoxy) -phenylisopropyl para-methoxybenzyl alkyl amine of the formula:

CH3 R wherein R is a lower-alkyl radical containing up to and including four carbon atoms.

4. A beta-(ortho-methoxy) phenyl-isopropyl para-methoxybenzyl alkyl amine of the formula:

CHs wherein R is a lower-alkyl radical containing up to and including four carbon atoms.

5. Beta (0rtho-meth0xy)pheny1 isopropyl para-methoxybenzyl methyl amine.

6. Beta (ortho-methoxy)phenyl isopropyl para-methoxy-benzyl methyl amine hydrochloride.

7. Beta (ortho-methoxy)phenyl isopropyl para-methoxybenzyl isopropyl amine.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,006,114 Rosenmund et a1. June 25, 1935 2,276,618 Kulz Mar. 17, 1942 2,317,012 Woodrufi Apr. 20, 1943 2,317,013 Woodrufi Apr. 20, 1943 2,450,497 Beidermann Oct. 5, 1948 2,504,122 Goodson Apr. 18, 1950 OTHER REFERENCES vol. 59, Pp 726- 

1. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF (1) BETA-(ORTHO-METHOXY) PHENYL-ISOPROPYL PARA-METHOXYBENZYL ALKYL AMINES OF THE FORMULA: 